The present invention relates to a fuel injection system for a gas turbine engine, more particularly such a system having a venturi to separate air flows issuing from air swirlers.
Present day fuel injection systems for gas turbine engines may utilize a venturi to enhance the mixing of the atomized fuel emanating from a fuel injector and air issuing from one or more air swirlers. In such known systems, the fuel emanating from the fuel injector has a generally conical configuration and typically impacts against the inner wall of the venturi. Such impact with the venturi wall causes a portion of the fuel to run down the wall of the venturi and be reinjected and reatomized at the exhaust of the venturi under the aerodynamic conditions in this exhaust zone. Such effects usually lead to the enlargement of the angle of the fuel cone at the venturi exhaust. Additionally, the contact between the atomized fuel and the venturi wall changes the size of the atomized fuel droplets thereby degrading the inherent atomizing ability of the fuel injector.
Known fuel injection systems may include a fuel injector having a primary fuel circuit which is operative throughout the operational range of the gas turbine engine and injects atomized fuel in a conical configuration, and a secondary fuel circuit which injects atomized fuel only when the gas turbine engine operating parameters exceed predetermined threshold values. The atomized fuel-cone configurations for both of the fuel circuits typically projects unvaporized fuel onto the walls of the primary combustion zone of the combustion chamber. The cooling air system for cooling the combustion chamber walls tends to constrain the combustion reaction within the primary combustion zone and, as a result, large quantities of unburned carbon monoxides (CO) and hydrocarbons (CH.sub.x) are generated.